Zonal isolation refers to the isolation of a subterranean formation or zone from other subterranean formations. The subterranean formation or zone may serve as a source of a natural resource such as oil, or water. To achieve isolation of a subterranean formation, a wellbore is typically drilled down to the subterranean formation while circulating a drilling fluid through the wellbore. After the drilling is terminated, a string of pipe (e.g., casing) is run in the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass, thereby attaching the string of pipe to the walls of the wellbore and sealing the annulus. Subsequent secondary cementing operations such as squeeze cementing may also be performed.
The physical characteristics of a cement are generally due to the nature of the cementious materials formed as a result of the reaction of cement with water, that is, the hydration of the cement. As hydration occurs, the cement develops various phases which impart physical characteristics (e.g., strength) to the cement. Once the cement is mixed with water, the hydration process begins and continues for so long as cementitious material and water are present in reactive forms and quantities.
Thus an ongoing need exists for improved cement compositions and methods of using same.